16. Examination and renovation: bearings and oil seals
Ball bearings should be washed thoroughly to remove all traces of oil
then tested as follows. Hold the outer race firmly and attempt to move
the inner race up and down, then from side to side. Examine the bearing
balls, cages and tracks, looking for signs of pitting or other damage.
Finally spin the bearings hard; any roughness caused by wear or damage
will be felt and heard immediately. If any free play, roughness or other
damage is found the bearing must be removed.
Roller bearings are checked in much the same way, except that free
play can be checked only in the up and down direction with the
components concerned temporarily reassembled. Remember that if a roller
bearing fails it may well mean having to replace, as well as the bearing
itself. one or two components which form its inner and outer races. If
in doubt about a roller bearing's condition, renew it.
Do not waste time checking oil seals; discard all seals and O-rings
disturbed during dismantling work and fit new ones on reassembly.
Considering their habit of leaking once disturbed, and the amount of
time and trouble necessary to replace them, they are relatively cheap if
renewed as a matter of course whenever they are disturbed.